Switching power supply is a power supply that uses an electronic circuit to control the time ratio of on and off of a switching element and to maintain a stable output voltage.
The switching power supply can have a rectifying circuit, a smoothing circuit, a switching element, a transformer, an output side rectifying circuit, and a central control device, etc. The rectifying circuit and the smoothing circuit can rectify and smooth an input alternating current; the central control device may have an on/off control port which can output a control signal to control on and off of the switching element, so that the smoothed electrical signal resonates; the transformer causes the resonant electrical signal to be transmitted to the output side of the switching power supply; the output side rectifying circuit rectifies the electrical signal transmitted to the output side of the switching power supply to form an output electrical signal for output.
Generally, the central control device may further have a resonant frequency control port and an impedance between the resonant frequency control port and a ground of the switching power supply can control the resonant frequency of the switching power supply during work and the resonant frequency can affect the output current value of the switching power supply. The central control device may be a semiconductor integrated circuit such as an Infineon ICL5101 chip.
FIG. 1 is a schematic view of a central control device of a prior art. As shown in FIG. 1, on/off control ports 2 and 3 of a central control device 1 can be connected to switching elements 4 and 5 respectively. Moreover, resistors R50 and R35 are connected between a resonant frequency control port 9 of the central control device 1 and the ground GND, wherein the resistors R50 and R35 are used to control the resonant frequency of the switching power supply during work.
It should be noted that the above introduction to technical background is merely for the purpose of a clear and complete description of the technical solutions of the present application and for a better understanding by those of ordinary skill in the art. The above technical solutions should not be considered to be well-known to those of ordinary skill in the art simply because these solutions are set forth in the section of background art of the present application.